High molecular weight polymers are widely used for increasing the viscosity of solutions in numerous fields, such as the oil and paper industries, water treatment, the mining, cosmetics and textile industries and generally in all the industrial techniques using thickened solutions. Now, these high molecular weight polymers have the drawback of having a low permanent shear strength with respect to the same polymers of smaller size. These shearing constraints on the high molecular weight polymers lead to macromolecular chain cleavages. The polymer thus degraded no longer has thickening properties, and the viscosity of the solutions containing it drops irreversibly. This loss of permanent shear strength leads to a degradation of the properties of the solutions based on high molecular weight polymers.
The Applicant set himself the objective of the formulation of novel additives which would be more stable under shearing compared to the compounds of the prior art. This objective is achieved thanks to novel additives which are associative and exchangeable in a thermoreversible manner. The associated (potentially cross-linked) and exchangeable copolymers of the invention have the advantage of being more stable to shear stresses. This characteristic results from the combined use of two particular compounds, a statistical copolymer bearing diol functions and a compound comprising at least two boronic ester functions.
Polymers, of which at least one monomer comprises boronic ester functions are known from document WO2013147795. These polymers are used for the production of electronic devices, in particular for devices in which it is desired to obtain a flexible user interface. These polymers are also used as synthesis intermediates. They allow the functionalization of the polymers by coupling with luminescent groups, electron-transporter groups, etc. The coupling of these groups is carried out by standard organic chemistry reactions, involving the boron atom, such as for example Suzuki coupling. However, no other use of these polymers, nor an association with other compounds is envisaged.
A copolymer resulting from the copolymerization of a methyl methacrylate (MMA) monomer and a glyceryl methacrylate monomer optionally protected by a boronic ester (namely butyl boronic acid adduct of glyceryl methacrylate (BBA-GMA)) is known from document U.S. Pat. No. 4,401,797. This copolymer forms a hydrogel in the presence of water and is used for the production of contact lenses. However, no other use of this copolymer in the field of lubricating compositions, nor an association via exchangeable chemical bonds with other compounds is envisaged.
Document EP0570073 discloses an additive which improves the viscosity index of a lubricating composition in which it is added. This additive is a copolymer resulting from the polymerization of 1-(methacryloylethoxy)-4,4,6-trimethyl-dioxaborinane and a methacrylate of a linear (C12-C18) alkyl. This additive belongs to the family of the borate compounds which can be represented by the general formula B(OR)3 with R an alkyl or aryl group. This additive does not belong to the family of the boronate compounds which can be represented by the general formula R—B(OR)2 with R an alkyl or aryl group. This additive cannot be associated with other compounds via exchangeable chemical bonds.
The Applicant also set himself the objective of the synthesis of novel polymers making it possible to increase the viscosity of solutions comprising them compared with the polymers of the prior art. In particular, his objective is to provide novel rheological additives the behaviour of which, when they are introduced into a solution, in particular into a hydrophobic solution, is opposite as regards temperature change compared with the behaviour of the solution and the polymer-type rheological additives of the prior art. This objective is achieved thanks to novel rheological additives capable of associating, in order to possibly form a gel, and exchanging chemical bonds in a thermoreversible manner. The additives of the present invention have the advantage of increasing the viscosity of the solution comprising them when the temperature increases.
Firstly, the Applicant attempted to synthesize copolymers bearing diol functions from commercial compounds such as solketal methacrylate marketed by Sigma-Aldrich®. However, the use of this monomer presents several drawbacks:                its purchase price is high;        the polarity of the solketal methacrylate and 2,3-dihydroxypropyl methacrylate units (resulting from the deprotection of the solketal function) limits the solubility of the copolymers in apolar mediums;        the pendant diol function is difficult to access on the copolymers;        depending on the nature of the copolymer, deprotection of the monomer once polymerized can be difficult and/or lead to the formation of gels.        
Thus, the Applicant also set himself the objective of the synthesis of novel statistical copolymers bearing diol functions which overcome the drawbacks mentioned above. This objective is achieved thanks to the novel polydiol statistical copolymers A1 comprising at least one monomer M1 of general formula (I) as described hereafter. The polydiol statistical copolymers A1 of the invention have in particular the following advantages:                deprotection of the protected diol functions once polymerized is simpler due to their greater accessibility;        they are more easily soluble in an apolar medium;        these polymers are adaptive, i.e. they are capable of responding to an external stimulus by a change of properties;        they can associate and exchange in a thermoreversible manner with compounds having at least two boronic ester functions, in particular in an apolar medium, for example.        
Secondly, the Applicant attempted to synthesize compounds bearing at least two boronic ester functions from commercial compounds such as 4-vinylphenylboronic acid marketed by Sigma-Aldrich®. However, the use of this compound presents several drawbacks:                the polymerization of these monomers in a hydrophobic medium leads to the formation of gels which are not compatible with the desired use;        the copolymers containing acid 4-vinylphenylboronic functions are not temperature stable in a hydrophobic medium and lead to the formation of gels.        
Thus, the Applicant also set himself the objective of the synthesis of novel compounds bearing at least two boronic ester functions which overcome the drawbacks mentioned above. This objective is achieved thanks to the novel compounds having at least two boronic ester functions of general formula (III), or comprising at least one monomer M3 of general formula (IV), as described hereafter. The compounds of the invention having at least two boronic ester functions have in particular the following advantages:                their syntheses are simple and inexpensive;        they are soluble in a hydrophobic medium, in particular in an apolar hydrophobic medium;        they do not form a gel during polymerization;        they are temperature stable in a hydrophobic medium and do not lead to the formation of gels.        